Betatrophin对TNFalpha或IL-1beta诱导NF-kappaB活化的负调控机制研究

Nonresolving inflammation, which is closely associated with the dysregulation of inflammation, is a key driver of multiple major diseases. NF-kB is a transcription factor that plays pivotal roles in the regulation of inflammation through responding to various stimuli and lead to the expression of various inflammatory proteins. Therefore, the normal activity of NF-kB is critical to the prevention and control of major inflammation-related diseases. Betatrophin is a newly identified secreted protein which is involved in glucose and lipid metabolisms, its relationship with the regulation of NF-kB activation has not been reported. In our pilot study, we found the expression level of Betatrophin was positively associated with the progression of type 2 diabetes, moreover, it could be induced by the pro-inflammatory cytokine TNFa. In addition, we found Betatrophin could inhibit TNFa- or IL-1b-induced NF-kB activation, and such effects may be mediated by targeting IKK kinase complex. In this study, we propose to identify the molecular target of Betatrophin in its inhibition of TNFa- or IL-1b-induced NF-kB activation, to investigate its regulation mechanisms and study whether Betatrophin has any effect in insulin signal pathway through regulating the activity of NF-kB. This work may reveal a new molecular mechanism of the regulation of NF-kB activation, and provide new insights into the mechanisms for inflammatory diseases such as diabetes.

非可控炎症是糖尿病、癌症等多种重大疾病的主要诱因，调控紊乱是造成炎症处于非可控状态的重要原因。NF-kB能诱导一系列炎症相关蛋白表达，在炎症反应调控中发挥核心作用，其活性的正常维持对相关疾病防治有重要意义。Betatrophin是一个新发现的参与糖脂代谢的分泌蛋白，但其是否参与NF-kB活性调控尚无报道。申请人前期工作发现该蛋白的表达不仅在2型糖尿病患者血清中随病情恶化上调，且在细胞水平受糖尿病相关促炎症因子TNFa的诱导，并能抑制TNFa或IL-1b诱导的NF-kB激活，该作用可能是通过在细胞内对IKK激酶复合物等靶标的调控介导。本项目计划进一步锁定Betatrophin的分子靶标，解析其调控NF-kB激活的具体机制，探讨其是否通过调控NF-kB活性而影响胰岛素通路。该研究有望揭示一种NF-kB活性调控的新机制，从而为糖尿病等炎症相关疾病的治疗提供理论依据。

炎症调控紊乱与败血症、糖尿病、癌症等多种疾病密切相关。转录因子NF-κB是炎症反应的核心控制因子，其活性的正常维持对相关疾病防治具有重大意义。本项目基于前期发现的Betatrophin/类血管生成素8(angiopoietin-like 8, ANGPTL8, 此为该分子的最新学术界统一名称)这一糖脂代谢的调控蛋白对NF-κB活性的抑制作用，进一步挖掘其作用机理。结果表明：炎症刺激可以诱导ANGPTL8的表达，敲低或敲除ANGPTL8可以促进TNFα诱导的NF-κB活化。在机理上讲，TNFα刺激后，ANGPTL8可协助自噬受体p62与IKK激酶复合物的调节亚基——IKKγ形成复合物，促进IKKγ经选择性自噬途径降解，从而下调NF-κB的活化水平。ANGPTL8的N端26-70区段所介导的ANGPTL8自身聚集作用对这一降解过程是必需的。此外，血液中ANGPTL8的表达水平在炎症性疾病的病人中显著上调，ANGPTL8/p62-IKKγ这个负反馈调控轴在LPS注射后的小鼠肝脏中也存在。相关结果项目负责人2017年以第一作者身份发表于国际一流杂志Nature Commnications。综上，本项目揭示了一种全新的NF-κB活性的负反馈调节机制，扩展了选择性自噬在炎症反应中的作用，也加深了人们对炎症反应与代谢调控分子交谈的理解，在基础研究领域具有较强的科学意义。同时，ANGPTL8的单克隆抗体是治疗冠心病等心血管疾病的重要前药，炎症反应作为机体的基础免疫反应，因此本研究也为相关药物开发工作提供一定参考。